docs: update DEVELOPMENT.md with SQL development guidelines

Add "Adding SQL" section to DEVELOPMENT.md with guidelines for:
- Modular SQL file organization
- Operator wrappers vs implementation separation
- Dependency declarations using REQUIRE comments
- Test file naming conventions
- Build system usage with tsort

Provides clear guidance for contributors developing new SQL features.

Author: tobyhede

DEVELOPMENT.md

@@ -318,6 +318,17 @@ This produces two SQL files in `releases/`:
 
 ## Structure
 
+### Adding SQL
+
+When adding new SQL files to the project, follow these guidelines:
+
+- Never drop the configuration table as it may contain customer data and needs to live across EQL versions
+- Everything else should have a `DROP IF EXISTS`
+- Functions should be `DROP` and `CREATE`, instead of `CREATE OR REPLACE`
+  - Data types cannot be changed once created, so dropping first is more flexible
+- Keep `DROP` and `CREATE` together in the code
+- Types need to be dropped last, add to the `666-drop_types.sql`
+
 ### Schema
 
 EQL is installed into the `eql_v2` PostgreSQL schema.